Sounding Grumpy Or ‘Short’

I’m most probably having more of a vent than asking advice. Im always being accused of sounding grumpy or being ’short’ with people, I’m not, my voice is quite deep and can be very monotone.

I know internally that I’m not  answering abruptly, I admit I can get tired quite quickly when in conversation, having to repeat a sentence when misheard can cause me to literally runout of words. It’s then thought that I’m being more awkward. I’m putting more energy into trying to smile and undulate my voice, if that’s the correct word? 

Im thinking it must run along the same lines as Martins post on looking miserable when not.

Is this something anyone else has encountered or am I being weirder than normal?